It is indicated in the literature (U.S. Pat. No. 4,596,874; J. Chem. Soc., Chem. Commun., 1984, 874; and J. Org. Chem., 1990, 55, 1736) that oxidation of secondary amines with hydrogen peroxide and sodium tungstate gives good yields of nitrones. However, when using dimethylamine in this manner, a considerable amount of N,N-dimethylformamide was produced as a co-product.